Pressure detection device

ABSTRACT

Provided is a pressure detection device which includes a pressure detection unit and a flow passage unit. The pressure detection unit includes a pressure sensor including a diaphragm and a first connection portion joined to the diaphragm. The flow passage unit includes a diaphragm and a second connection portion joined to the diaphragm. One of the first connection portion and the second connection portion is formed of a magnet, and the other of the first connection portion and the second connection portion is formed of a magnet or a magnetic body. In a state where the flow passage unit is mounted on the pressure detection unit, the first connection portion and the second connection portion are disposed in a state where the first connection portion and the second connection portion are attracted to each other by a magnetic force.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application No.2017-031290, the contents of which are incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present invention relates to a pressure detection device whichdetects a pressure of a fluid flowing through a flow passage.

BACKGROUND ART

Conventionally, there is known an inline pressure sensor where a bodyand a sensor body are formed into one integral body, wherein a flowpassage, through which a liquid such as a liquid medicine is made toflow, is formed in the body, and the sensor body detects a pressure ofthe liquid which is transmitted to a pressure receiving surface througha protective sheet (see Japanese Unexamined Patent Application,Publication No. 2005-207946 (hereinafter referred to as PatentLiterature 1), for example).

The pressure sensor disclosed in Patent Literature 1 is configured todetect a pressure of a fluid which is transmitted to the sensor bodythrough the protective sheet mounted on a lower surface of the sensorbody.

SUMMARY Technical Problem

The pressure sensor disclosed in Patent Literature 1 can acquire adetection value, which corresponds to a pressure at which a fluidpresses the protective sheet, when the protective sheet is pressed tothe lower surface of the sensor body by the pressure of the fluid.

However, the pressure sensor disclosed in Patent Literature 1 cannotacquire a detection value which corresponds to a pressure (negativepressure) of a fluid when the pressure of the fluid lowers so that theprotective sheet receives a force by which the protective sheet isseparated from the lower surface of the sensor body. This is because thepressure sensor disclosed in Patent Literature 1 is an electrostaticcapacitance type pressure sensor or a piezoelectric type pressure sensorwhich acquires, as a detection value, a force by which the lower surfaceof the sensor body is pressed. Accordingly, the pressure sensordisclosed in Patent Literature 1 cannot detect a pressure of a fluidwith accuracy when the pressure of the fluid is a negative pressure.

Further, in the pressure sensor disclosed in Patent Literature 1, thebody in which the flow passage is formed and the sensor body are formedinto one integral body. Accordingly, in changing a liquid forming adetection target, it is necessary to wash the existing flow passage withpure water or the like.

However, it is difficult to completely remove a liquid remaining in theflow passage with the method of washing the flow passage and, at thesame time, such a method requires a lot of time for performing a washingoperation. Accordingly, for example, in a medical field, a biotechnologyfield or the like which requires a flow passage where the inside of theflow passage is sterilized or the like thus being completely clean, themethod of washing the flow passage in changing a liquid is notsufficient in view of smoothness and safety of operation.

The present disclosure has been made under such circumstances, and it isan object of the present disclosure to provide a pressure detectiondevice where smoothness and safety of operation of changing a fluid tobe introduced into a flow passage are enhanced, and a pressure of afluid can be detected with accuracy even when the pressure of the fluidis a negative pressure.

Solution to Problem

To solve the above-mentioned problem, the present disclosure adopts thefollowing solutions.

A pressure detection device includes: a pressure detection unitconfigured to detect a pressure transmitted to a pressure detectingportion; a flow passage unit in which a flow passage for introducing afluid is formed; and a mounting mechanism configured to detachably mountthe flow passage unit on the pressure detection unit. The pressuredetection unit includes: a pressure sensor including the pressuredetecting portion; and a first connection portion joined to the pressuredetecting portion. The flow passage unit includes: a pressure receivingportion configured to be displaced by receiving a pressure of the fluidflowing through the flow passage; and a second connection portion joinedto the pressure receiving portion. One of the first connection portionand the second connection portion is formed of a magnet, and the otherof the first connection portion and the second connection portion isformed of a magnet or a magnetic body. In a state where the flow passageunit is mounted on the pressure detection unit by the mountingmechanism, the first connection portion and the second connectionportion are disposed in a state where the first connection portion andthe second connection portion are attracted to each other by a magneticforce.

According to the pressure detection device of one aspect of the presentdisclosure, the flow passage unit is detachably mounted on the pressuredetection unit by the mounting mechanism. Accordingly, to change a fluidto be introduced into the flow passage, the flow passage unit which isalready used is removed from the pressure detection unit, and a flowpassage unit which is unused can be newly mounted on the pressuredetection unit.

With such a configuration, in changing a fluid to be introduced into theflow passage, it becomes unnecessary to perform a washing operation ofthe flow passage, which requires a lot of time, so that smoothness ofthe operation can be improved. Further, a flow passage unit which isunused can be newly used and hence, safety can be improved.

Further, according to the pressure detection device of one aspect of thepresent disclosure, in a state where the flow passage unit is mounted onthe pressure detection unit by the mounting mechanism, the firstconnection portion joined to the pressure detecting portion and thesecond connection portion joined to the pressure receiving portion aredisposed in a state where the connection portions are attracted to eachother by a magnetic force. Accordingly, when a pressure of a fluidflowing through the flow passage is a positive pressure, the secondconnection portion joined to the pressure receiving portion is separatedfrom the flow passage side due to the pressure of the fluid, and thesecond connection portion presses the first connection portion to thepressure detecting portion. With such pressing, the pressure of thefluid is detected as a positive pressure by the pressure detectingportion.

On the other hand, when a pressure of a fluid flowing through the flowpassage is a negative pressure, the second connection portion joined tothe pressure receiving portion is attracted to the flow passage side dueto the pressure of the fluid, and the second connection portion attractsthe first connection portion, which is connected to the secondconnection portion by a magnetic force, to the flow passage side. Withsuch attraction, the pressure of the fluid is detected as a negativepressure by the pressure detecting portion.

As described above, according to the pressure detection device of oneaspect of the present disclosure, it is possible to provide a pressuredetection device where smoothness and safety of an operation of changinga fluid to be introduced into the flow passage are improved, and apressure of a fluid can be detected with accuracy even when the pressureof the fluid is a negative pressure.

In the pressure detection device according to one aspect of the presentdisclosure, the first connection portion may be formed of a magnet, andthe second connection portion may be formed of a magnetic body.

The flow passage unit, which is exchanged after being used, is formed ofa magnetic body, which is relatively cheap. Accordingly, running costcan be reduced when the pressure detection device is continuously used.

In the pressure detection device according to one aspect of the presentdisclosure, an end surface of the first connection portion on a side ofthe flow passage unit may be formed to have a planar shape, and an endsurface of the second connection portion on a side of the pressuredetection unit may be formed to have a spherical shape which projectstoward the first connection portion.

With such a configuration, the first connection portion and the secondconnection portion are connected with each other only at one point of aspherical distal end of the first connection portion. Accordingly, aposition where a pressure is transmitted between the first connectionportion and the second connection portion is fixed to one point.Therefore, it is possible to prevent a problem that a position where apressure is transmitted between the first connection portion and thesecond connection portion changes so that an error occurs in pressuredetection value.

In the pressure detection device according to one aspect of the presentdisclosure, the second connection portion may be disposed in an innerspace defined by the pressure receiving portion and the pressuredetecting portion, the first connection portion may be joined to asurface of the pressure detecting portion which is not in contact withthe inner space, and in a state where the flow passage unit is mountedon the pressure detection unit by the mounting mechanism, the firstconnection portion and the second connection portion may be disposed ina state where the first connection portion and the second connectionportion are attracted to each other by a magnetic force with thepressure detecting portion interposed between the first connectionportion and the second connection portion.

According to the pressure detection device having such a configuration,the first connection portion is joined to a surface of the pressuredetecting portion on the side which is not in contact with the innerspace. With such a configuration, in removing the flow passage unit fromthe pressure detection unit, a magnetic force in the direction that thefirst connection portion approaches the pressure detecting portion actson a portion where the first connection portion and the pressuredetecting portion are joined to each other. Accordingly, compared to thecase where the first connection portion is joined to a surface of thepressure detecting portion on the side which is in contact with theinner space, it is possible to prevent, by the action of a magneticforce, a problem that the first connection portion is peeled off fromthe pressure detecting portion. Further, there is no possibility that amanipulator inadvertently comes into contact with the portion where thefirst connection portion and the pressure detecting portion are joinedto each other. Accordingly, it is possible to prevent a problem that thefirst connection portion is peeled off from the pressure detectingportion due to carelessness of the manipulator.

In the pressure detection device according to one aspect of the presentdisclosure, the pressure detection unit may have a communication flowpassage configured to make the inner space defined by the pressurereceiving portion formed into a film shape and the pressure detectingportion formed into a film shape and an outer space maintained at anatmospheric pressure communicate with each other.

With such a configuration, the inner space defined by the pressurereceiving portion of the flow passage unit and the pressure detectingportion of the pressure detection unit is maintained at an atmosphericpressure. Accordingly, the pressure detecting portion can detect apressure of a fluid with accuracy.

Advantageous Effects

According to the present disclosure, it is possible to provide apressure detection device where smoothness and safety of operation ofchanging a fluid to be introduced into a flow passage are enhanced, anda pressure of a fluid can be detected with accuracy even when thepressure of the fluid is a negative pressure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial longitudinal cross-sectional view showing a pressuredetection device of a first embodiment.

FIG. 2 is a partial longitudinal cross-sectional view showing thepressure detection device where a flow passage unit is removed from apressure detection unit.

FIG. 3 is a partially enlarged view of a portion I of the pressuredetection device shown in FIG. 1.

FIG. 4 is a cross-sectional view of the flow passage unit and a nutshown in FIG. 3 as viewed from an arrow II-II.

FIG. 5 is a bottom view of the flow passage unit and the nut shown inFIG. 4.

FIG. 6 is a partially enlarged view showing a pressure detection deviceof a second embodiment.

FIG. 7 is a partially enlarged view showing a pressure detection deviceof a third embodiment.

FIG. 8 is a partially enlarged view showing a pressure detection deviceof a fourth embodiment.

FIG. 9 is a partially enlarged view showing a modification of thepressure detection device of the fourth embodiment.

FIG. 10 is a partially enlarged view showing another modification of thepressure detection device of the fourth embodiment.

FIG. 11 is a partially enlarged view showing a pressure detection deviceof a fifth embodiment.

FIG. 12 is a partially enlarged view showing a pressure detection deviceof a sixth embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a pressure detection device 100 according to a firstembodiment of the present disclosure is described with reference todrawings.

As shown in FIG. 1, the pressure detection device 100 of this embodimentincludes: a pressure detection unit 10 mounted on an installationsurface S by fastening bolts (not shown in the drawing); a flow passageunit 20 in which a flow passage 21 a is formed; and a nut 30 (mountingmechanism) for detachably mounting the flow passage unit 20 on thepressure detection unit 10.

As shown in FIG. 1, the pressure detection unit 10 is mounted on theinstallation surface S, and the flow passage unit 20 is mounted on thepressure detection unit 10 by the nut 30. The pressure detection device100 is mounted on the installation surface S in a state where the flowpassage unit 20 is mounted on the pressure detection unit 10 by the nut30 thus forming an integral body.

Next, the pressure detection unit 10 is described in detail. Thepressure detection unit 10 is a device which detects a pressuretransmitted to a diaphragm 12 a. The pressure detection unit 10includes: a first connection portion 11; a pressure sensor 12; a bodyportion 13 for accommodating the pressure sensor 12; a sensor holdingportion 14 for holding the pressure sensor 12 in a state where thepressure sensor 12 is disposed in the body portion 13; a sensor board(not shown in the drawing) for transmitting power and an electric signalbetween the pressure sensor 12 and a cable 200; and a housing 17 foraccommodating the sensor board. The cable 200 electrically connects thesensor board and a control device disposed outside the pressuredetection device 100 with each other.

The first connection portion 11 is formed of a permanent magnet formedinto a cylindrical shape along an axis Y1. The first connection portion11 is made of neodymium or the like, for example. The first connectionportion 11 is joined to the diaphragm 12 a of the pressure sensor 12 byan adhesive agent (epoxy resin based adhesive agent, for example). Asshown in FIG. 3, an end surface of the first connection portion 11 onthe flow passage unit 20 side is formed to have a planar shape disposedon a plane which is orthogonal to the axis Y1. The first connectionportion 11 attracts a second connection portion 23, which is formed of amagnetic body, by a magnetic force of the permanent magnet, and thefirst connection portion 11 maintains a state where the first connectionportion 11 is in contact with the second connection portion 23. Thesecond connection portion 23, which the flow passage unit 20 includes,is described later.

In the description made heretofore, the first connection portion 11 isformed of a permanent magnet, and the second connection portion 23 isformed of a magnetic body. However, another mode may be adopted. Forexample, each of both the first connection portion 11 and the secondconnection portion 23 may be formed of a permanent magnet.Alternatively, the first connection portion 11 may be formed of amagnetic body, and the second connection portion 23 may be formed of apermanent magnet. As described above, in the pressure detection device100 of this embodiment, one of the first connection portion 11 and thesecond connection portion 23 is formed of a magnet, and the other of thefirst connection portion 11 and the second connection portion 23 isformed of a magnet or a magnetic body.

Hereinafter, an example is described where the first connection portion11 is formed of a permanent magnet, and the second connection portion 23is formed of a magnetic body.

As shown in FIG. 3 (a partially enlarged view of a portion I in FIG. 1),the pressure sensor 12 includes: the diaphragm 12 a (pressure detectionsurface) formed into a thin film shape using a material having corrosionresistance (for example, sapphire); a strain resistance (not shown inthe drawing) adhered to the diaphragm 12 a; and a base portion 12 cwhich holds the diaphragm 12 a.

The pressure sensor 12 is a strain type sensor. The strain type sensoroutputs a pressure signal which corresponds to a change in resistancevalue of the strain resistance which deforms corresponding to a pressuretransmitted to the diaphragm 12 a. A through hole 12 b, whichcommunicates with the diaphragm 12 a, is formed in the base portion 12 cso that one surface (a surface on the lower side in FIG. 3) of thediaphragm 12 a is maintained at an atmospheric pressure. Accordingly,the pressure sensor 12 is a sensor which detects a gauge pressure usingan atmospheric pressure as a reference.

The body portion 13 is a member which accommodates the pressure sensor12 therein, and on which the flow passage unit 20 is mounted by the nut30. The body portion 13 is made of a metal material such as SUS304, forexample. As shown in FIG. 3, a communication flow passage 12 d is formedin the body portion 13. The communication flow passage 12 d allows aninner space S1 and an outer space S2 to communicate with each other. Theinner space S1 is defined by a diaphragm 22 which the flow passage unit20 includes and the diaphragm 12 a which the pressure sensor 12includes. The outer space S2 is maintained at an atmospheric pressure.

As shown in FIG. 1 and FIG. 2, the sensor holding portion 14 is a memberwhich is formed into a cylindrical shape about an axis Y1 (first axis),and male threads are formed on an outer peripheral surface of the sensorholding portion 14. In a state where the pressure sensor 12 is disposedin an inner peripheral side of the body portion 13, the male threadsformed on the outer peripheral surface of the sensor holding portion 14are fastened to female threads formed on an inner peripheral surface ofthe body portion 13 so that the sensor holding portion 14 holds thepressure sensor 12 in the body portion 13.

The sensor board (not shown in the drawing) includes: an amplifiercircuit (not shown in the drawing) for amplifying a pressure signaloutputted by the pressure sensor 12; an interface circuit fortransmitting the pressure signal, which is amplified by the amplifiercircuit, to a pressure signal line (not shown in the drawing) of thecable 200; a power supply circuit (not shown in the drawing) fortransmitting a power supply voltage supplied from the outside throughthe cable 200 to the pressure sensor 12; a zero-point adjustment circuit(not shown in the drawing) for performing a zero-point adjustment when azero-point adjustment switch (not shown in the drawing) is pressed andthe like.

The zero-point adjustment circuit is a circuit which performs anadjustment such that, when the zero-point adjustment switch (not shownin the drawing) is pressed by a manipulator, a pressure signal to beoutputted by the pressure sensor 12 at the point is set as an initialvalue (zero).

Next, the flow passage unit 20 is described in detail.

As shown in FIG. 3 to FIG. 5, the flow passage unit 20 includes a flowpassage body 21, the diaphragm (pressure receiving portion) 22, and thesecond connection portion 23.

In this embodiment, FIG. 4 is a cross-sectional view of the flow passageunit 20 and the nut 30 shown in FIG. 3 as viewed from an arrow II-II.Further, FIG. 5 is a bottom view of the flow passage unit 20 and the nut30 shown in FIG. 4 as viewed from below.

The flow passage body 21 is a member where the flow passage 21 a isformed therein. A fluid is made to flow through the flow passage 21 a inthe flow direction extending along an axis X1 from an inflow port 21 bto an outflow port 21 c. The flow passage body 21 is made ofpolycarbonate, for example. A fluid chamber 24, which opens to an areabelow the flow passage unit 20, is formed at a substantially centerposition of the flow passage body 21 in the direction of the axis X1.The fluid chamber 24 is a space having a circular cross section, whichis orthogonal to the axis Y1. The fluid chamber 24 forms a portion ofthe flow passage 21 a.

An inflow side pipe (not shown in the drawing), through which a fluid ismade to flow in the inflow port 21 b, is mounted on the inflow port 21 bof the flow passage body 21. An outflow side pipe (not shown in thedrawing), through which the fluid flowing out from the outflow port 21 cflows, is mounted on the outflow port 21 c of the flow passage unit 20.A pressure of a fluid flowing through the flow passage 21 a from theinflow port 21 b to the outflow port 21 c is detected by the pressuredetection unit 10.

In this embodiment, a fluid means a liquid such as a culture solution,blood or a dialysate, for example. The flow passage unit 20 can beeasily mounted on and removed from the pressure detection unit 10 by thenut 30 described later. Accordingly, the pressure detection device 100of this embodiment is not provided with a mechanism for washing the flowpassage 21 a, and the flow passage unit 20, which includes the flowpassage 21 a, can be exchanged at a suitable timing. The pressuredetection device 100 having such a configuration is effectively usedparticularly in a medical field, a biotechnology field or the like whichrequires a flow passage where the inside of the flow passage issterilized or the like thus being completely clean.

Further, in FIG. 4, a fluid flows in from the inflow port 21 b, and thefluid flows out from the outflow port 21 c. However, another mode may beadopted. For example, the direction along which a fluid flows may bereversed by using the inflow port 21 b shown in FIG. 4 as an outflowport and by using the outflow port 21 c shown in FIG. 4 as an inflowport. Alternatively, it may be possible to adopt the configuration whereeither one of the inflow port 21 b or the outflow port 21 c is closed,and a pressure of a fluid introduced into the flow passage 21 a having aclosed terminal end is detected.

The diaphragm 22 is a member which is formed into a thin film shapeusing a material having corrosion resistance (for example, a siliconeresin material, or polycarbonate). The diaphragm 22 is a member formedinto a circular shape as viewed in a plan view using the axis Y1 as acenter axis. The diaphragm 22 is joined to a lower surface of the flowpassage body 21 by bonding or by welding. Accordingly, there is nopossibility that a fluid introduced into the fluid chamber 24 flows outto the outside from the fluid chamber 24. The diaphragm 22 is formedinto a thin film shape so that the diaphragm 22 is displaced in thedirection of the axis Y1 by receiving a pressure of a fluid flowingthrough the fluid chamber 24 forming the portion of the flow passage 21a.

The second connection portion 23 is formed of a magnetic body formedinto a cylindrical shape along the axis Y1, and is made of an ironmaterial such as S45C stipulated in the JIS standard. The secondconnection portion 23 is joined to a surface of the diaphragm 22 on thepressure detection unit 10 side by an adhesive agent (for example, epoxyresin based adhesive agent). As shown in FIG. 3, an end surface of thesecond connection portion 23 on the pressure detection unit 10 side isformed into a spherical shape which projects toward the first connectionportion 11 along the axis Y1. The second connection portion 23 isattracted by a magnetic force of the first connection portion 11 formedof a permanent magnet, and the second connection portion 23 ismaintained in a state where the second connection portion 23 is incontact with the first connection portion 11.

Next, the description is made with respect to a mechanism for mountingthe flow passage unit 20 on the pressure detection unit 10 using the nut30.

As shown in FIG. 2 and FIG. 4, the nut 30 is a member formed into acylindrical shape along the axis Y1. An endless annular projectingportion 31, which extends about the axis Y1, is formed on an innerperipheral surface of the nut 30. On the other hand, an endless annulargroove portion 25, which extends about the axis Y1, is formed on aportion of an outer peripheral surface of the flow passage unit 20 onthe lower end side. The nut 30 is made of an elastically deformablematerial (for example, resin material). The nut 30 is fitted by pressingon the portion of the outer peripheral surface of the flow passage unit20 on the lower end side so that the annular projecting portion 31 isengaged with the annular groove portion 25.

As shown in FIG. 2 and FIG. 4, in a state where the annular projectingportion 31 is engaged with the annular groove portion 25, an extremelysmall gap is formed between an inner peripheral surface of the annularprojecting portion 31 and an outer peripheral surface of the annulargroove portion 25. Accordingly, in a state where the nut 30 is mountedon the flow passage unit 20, the nut 30 is rotatable about the axis Y1with respect to the flow passage body 21. With such a configuration, anoperator can rotate the nut 30 about the axis Y1 in a state where theoperator holds the flow passage unit 20.

In mounting the flow passage unit 20 on the pressure detection unit 10installed to the installation surface S, the operator performs theoperation with the following procedure.

First, as shown in FIG. 2, the flow passage unit 20 is disposed suchthat a center axis of the flow passage unit 20 agrees with the axis Y1which is a center axis of the pressure detection unit 10. Then, the flowpassage unit 20 is moved downward along the axis Y1 so that the bodyportion 13 is inserted into a recessed portion 20 a formed at a lowerportion of the flow passage unit 20.

Next, the operator rotates the nut 30 about the axis Y1 in the fasteningdirection while gripping the flow passage unit 20. With such operations,female threads 32 formed on the inner peripheral surface of the nut 30are fastened to male threads 13 a formed on an outer peripheral surfaceof the body portion 13. By fastening the female threads 32 of the nut 30and the male threads 13 a of the pressure detection unit 10 to eachother, the second connection portion 23 of the flow passage unit 20gradually approaches and comes into contact with the first connectionportion 11 of the pressure detection unit 10. Accordingly, a state shownin FIG. 1 and FIG. 3 is brought about. The flow passage unit 20 ismounted on the pressure detection unit 10 as described above.

The procedure for mounting the flow passage unit 20 which is unused onthe pressure detection unit 10 has been described heretofore. Aprocedure for removing the flow passage unit 20 which is already usedfrom the pressure detection unit 10 is opposite to the proceduredescribed above.

The operator rotates the nut 30 about the axis Y1 in the fasteningrelease direction while gripping the flow passage unit 20 in a stateshown in FIG. 1. With such an operation, fastening between the femalethreads 32 of the nut 30 and the male threads 13 a of the pressuredetection unit 10 is released.

In the pressure detection device 100 of this embodiment, the firstconnection portion 11 joined to the diaphragm 12 a and the secondconnection portion 23 joined to the diaphragm 22 are brought intocontact with each other by fastening the female threads 32 of the nut 30and the male threads 13 a of the pressure detection unit 10 to eachother. Accordingly, it is possible to prevent that the first connectionportion 11 and the second connection portion 23 inadvertently come intocontact with each other thus damaging the diaphragm 12 a and thediaphragm 22.

As shown in FIG. 1 and FIG. 3, in the pressure detection device 100 ofthis embodiment, in a state where the flow passage unit 20 is mounted onthe pressure detection unit 10 by the nut 30, the second connectionportion 23 formed of a magnetic body is attracted by and comes intocontact with the first connection portion 11 by a magnetic force of thefirst connection portion 11 formed of a permanent magnet. Accordingly,when a pressure of a fluid in the fluid chamber 24 becomes a positivepressure, the diaphragm 22 is displaced downward along the axis Y1, andsuch a displacement is transmitted to the diaphragm 12 a through thesecond connection portion 23 and the first connection portion 11.

On the other hand, when a pressure of a fluid in the fluid chamber 24becomes a negative pressure, the diaphragm 22 is displaced upward alongthe axis Y1. The second connection portion 23 is maintained in a stateof being in contact with the first connection portion 11 by a magneticforce. Accordingly, when the diaphragm 22 and the second connectionportion 23 are attracted to the fluid chamber 24 side, the firstconnection portion 11 and the diaphragm 12 a are also attracted to thefluid chamber 24 side. For this reason, when the diaphragm 22 isdisplaced due to a negative pressure of a fluid in the fluid chamber 24,the diaphragm 12 a joined to the first connection portion 11 isattracted to the fluid chamber 24 side so that a resistance value of thestrain resistance changes to a value indicating a negative pressuretogether with the deformation of the diaphragm 12 a.

The description is made with respect to the manner of operation andadvantageous effects which the above-described pressure detection device100 of this embodiment can acquire.

According to the pressure detection device 100 of this embodiment, theflow passage unit 20 is detachably mounted on the pressure detectionunit 10 by the nut 30. Accordingly, to change a fluid which is made toflow through the flow passage 21 a, the flow passage unit 20 which isalready used is removed from the pressure detection unit 10, and a flowpassage unit 20 which is unused can be newly mounted on the pressuredetection unit 10.

With such a configuration, in changing a fluid which is made to flowthrough the flow passage 21 a, it becomes unnecessary to perform awashing operation of the flow passage 21 a, which requires a lot oftime, so that smoothness of the operation can be improved. Further, aflow passage unit 20 which is unused can be newly used and hence, safetycan be improved.

Further, according to the pressure detection device 100 of thisembodiment, in a state where the flow passage unit 20 is mounted on thepressure detection unit 10 by the nut 30, the first connection portion11 joined to the diaphragm 12 a and the second connection portion 23joined to the diaphragm 22 are disposed in a state where the connectionportions are brought into contact with each other by a magnetic force.Accordingly, when a pressure of a fluid flowing through the flow passage21 a is a positive pressure, the second connection portion 23 joined tothe diaphragm 22 is separated from the flow passage 21 a side due to thepressure of the fluid, and the second connection portion 23 presses thefirst connection portion 11 to the diaphragm 12 a. With such pressing,the pressure of the fluid is detected as a positive pressure by thestrain resistance of the diaphragm 12 a.

On the other hand, when a pressure of a fluid flowing through the flowpassage 21 a is a negative pressure, the second connection portion 23joined to the diaphragm 22 is attracted to the flow passage 21 a sidedue to the pressure of the fluid, and the second connection portion 23attracts the first connection portion 11, which is connected to thesecond connection portion 23 by a magnetic force, to the flow passage 21a side. With such attraction, the pressure of the fluid is detected as anegative pressure by the strain resistance of the diaphragm 12 a.

As described above, according to the pressure detection device 100 ofthis embodiment, it is possible to provide the pressure detection device100 where smoothness and safety of an operation of changing a fluidwhich is made to flow through the flow passage 21 a are improved, and apressure of a fluid can be detected with accuracy even when the pressureof the fluid is a negative pressure.

Further, in the pressure detection device 100 of this embodiment, thefirst connection portion 11 is formed of a magnet, and the secondconnection portion 23 is formed of a magnetic body.

The flow passage unit 20, which is exchanged after being used, is formedof a magnetic body, which is relatively cheap. Accordingly, running costcan be reduced when the pressure detection device 100 is continuouslyused.

In the pressure detection device 100 of this embodiment, the end surfaceof the first connection portion 11 on the flow passage unit 20 side isformed into a planar shape, and the end surface of the second connectionportion 23 on the pressure detection unit 10 side is formed into aspherical shape which projects toward the first connection portion 11.

With such a configuration, the first connection portion 11 and thesecond connection portion 23 are connected with each other only at onepoint of a spherical distal end of the first connection portion 11.Accordingly, a position where a pressure is transmitted between thefirst connection portion 11 and the second connection portion 23 isfixed to one point. Therefore, it is possible to prevent a problem thata position where a pressure is transmitted between the first connectionportion 11 and the second connection portion 23 changes so that an erroroccurs in pressure detection value.

In the pressure detection device 100 of this embodiment, the pressuredetection unit 10 includes the communication flow passage 12 d whichmakes the inner space S1, defined by the diaphragm 22 and the diaphragm12 a, and the outer space S2, maintained at an atmospheric pressure,communicate with each other.

With such a configuration, the inner space S1 defined by the diaphragm22 of the flow passage unit 20 and the diaphragm 12 a of the pressuredetection unit 10 is maintained at an atmospheric pressure. Accordingly,the diaphragm 12 a can detect a pressure of a fluid with accuracy.

Second Embodiment

Next, a pressure detection device according to a second embodiment ofthe present disclosure is described with reference to drawings.

The second embodiment is a modification of the first embodiment.Hereinafter, unless otherwise specified below, the second embodiment isassumed equal to the first embodiment so that the same constitutionalelements are given the same reference characters, and the description ofsuch constitutional elements is omitted.

The pressure detection device of the second embodiment differs from thefirst embodiment with respect to a point that a positioning hole 11Aa isformed on a first connection portion 11A joined to the diaphragm 12 a ofthe pressure detection unit 10.

As shown in FIG. 6, an end surface of the first connection portion 11Aon the flow passage unit 20 side is formed to have a planar shapedisposed on a plane which is orthogonal to the axis Y1. Further, thepositioning hole 11Aa is formed on an end surface of the firstconnection portion 11A on the flow passage unit 20 side.

The positioning hole 11Aa shown in FIG. 6 is a hole having a conicalinner surface which is recessed downward. As shown in FIG. 6, thepositioning hole 11Aa has a V shape which is recessed downward inlongitudinal cross section taken along the axis Y1. In a state where thesecond connection portion 23 is brought into contact with the firstconnection portion 11A by a magnetic force, a center position of aspherical end surface of the second connection portion 23 is disposed atthe position which agrees with the positioning hole 11Aa.

As shown in FIG. 6, a portion of the spherical end surface of the secondconnection portion 23 is accommodated in the positioning hole 11Aa atthe center position which agrees with the axis Y1. Accordingly, evenwhen an external force acts on the position where the first connectionportion 11A and the second connection portion 23 are brought intocontact with each other, the first connection portion 11A is hold suchthat the center position of the first connection portion 11A is notdisplaced from the position of the positioning hole 11Aa. With such aconfiguration, a pressure of a fluid which acts on the diaphragm 22 istransmitted to the diaphragm 12 a from the position which agrees withthe axis Y1 and hence, the diaphragm 12 a can detect the pressure of thefluid with accuracy.

Third Embodiment

Next, a pressure detection device according to a third embodiment of thepresent disclosure is described with reference to drawings.

The third embodiment is a modification of the first embodiment.Hereinafter, unless otherwise specified below, the third embodiment isassumed equal to the first embodiment so that the same constitutionalelements are given the same reference characters, and the description ofsuch constitutional elements is omitted.

The pressure detection device of the third embodiment differs from thefirst embodiment with respect to a point that a second connectionportion 23A which is joined to the diaphragm 22 of the flow passage unit20 has an end surface on the pressure detection unit 10 side which isformed into a planar shape.

As shown in FIG. 7, the end surface of the second connection portion 23Aon the pressure detection unit 10 side is formed to have a planar shapedisposed on a plane orthogonal to the axis Y1. Further, an end surfaceof the first connection portion 11 on the flow passage unit 20 side isformed to have a planar shape disposed on a plane orthogonal to the axisY1.

As described above, in the pressure detection device of the thirdembodiment, each of the end surface of the first connection portion 11and the end surface of the second connection portion 23A, whichopposedly face each other, has a planar shape. Accordingly, a contactarea between the end surface of the first connection portion 11 and theend surface of the second connection portion 23A when these end surfacescome into contact with each other increases thus increasing a contactforce, which is generated when the first connection portion 11 and thesecond connection portion 23A are brought into contact with each otherby a magnetic force. Accordingly, when the pressure detection device ofthis embodiment and the pressure detection device of the firstembodiment respectively adopt a permanent magnet having the samemagnetic force, the pressure detection device of this embodiment canhave a larger contact force between the first connection portion 11 andthe second connection portion 23A.

By increasing a contact force between the first connection portion 11and the second connection portion 23A which is joined to the diaphragm22, an attracting force by which the second connection portion 23Aattracts the first connection portion 11 increases when the diaphragm 22and the second connection portion 23A move in the direction along whichthe diaphragm 22 and the second connection portion 23A are separatedfrom the diaphragm 12 a. For this reason, when the first connectionportion 11 moves, it is possible to increase a distance where the firstconnection portion 11 can move while being in contact with the secondconnection portion 23A. Accordingly, the pressure detection device ofthis embodiment can increase a negative pressure measurement rangecompared to the pressure detection device of the first embodiment.

Fourth Embodiment

Next, a pressure detection device according to a fourth embodiment ofthe present disclosure is described with reference to drawings.

The fourth embodiment is a modification of the first embodiment.Hereinafter, unless otherwise specified below, the fourth embodiment isassumed equal to the first embodiment so that the same constitutionalelements are given the same reference characters, and the description ofsuch constitutional elements is omitted.

The pressure detection device of the fourth embodiment differs from thepressure detection device of the first embodiment with respect to apoint that a second connection portion 23B is formed of a magnetic body23Ba and a cover portion 23Bb made of a resin which accommodates themagnetic body 23Ba.

As shown in FIG. 8, the second connection portion 23B in this embodimentis formed of the magnetic body 23Ba and the cover portion 23Bb made of aresin which accommodates the magnetic body 23Ba. The magnetic body 23Bais joined to the diaphragm 22 by an adhesive agent. The cover portion23Bb is joined to the diaphragm 22 by an adhesive agent or by thermalwelding.

With respect to the second connection portion 23B in this embodiment,the magnetic body 23Ba is protected by the cover portion 23Bb so as notto be exposed to the inner space S1. Accordingly, with the provision ofthe second connection portion 23B in this embodiment, it is possible toprevent problems such as a problem that the magnetic body 23Ba and thefirst connection portion 11 come into contact with each other thuscausing wear of the magnetic body 23Ba and the first connection portion11, or a problem that the magnetic body 23Ba is exposed to the innerspace S1 thus causing corrosion of the magnetic body 23Ba.

The second connection portion 23B shown in FIG. 8 is formed such thatthe cover portion 23Bb covers only a periphery of the magnetic body23Ba. However, another mode may be adopted. For example, as in the caseof a second connection portion 23C shown in FIG. 9, it may be possibleto adopt a modification where a cover portion 23Cb made of a resincovers not only a periphery of a magnetic body 23Ca but also an entireend surface of the diaphragm 22 on the pressure detection unit 10 side.According to this modification, the entire end surface of the diaphragm22 on the pressure detection unit 10 side is covered by the coverportion 23Cb and hence, the diaphragm 22 can be protected. Further, itis possible to prevent a problem that the magnetic body 23Ca is peeledoff from the diaphragm 22.

It is also possible to adopt another modification where, in addition tothe configuration of the second connection portion 23C shown in FIG. 9,a first connection portion 11B is formed of a permanent magnet 11Ba anda cover portion 11Bb made of a resin which accommodates the permanentmagnet 11Ba.

As shown in FIG. 10, with respect to the first connection portion 11B inanother modification, the permanent magnet 11Ba is protected by thecover portion 11Bb so as not to be exposed to the inner space S1.Accordingly, with the provision of the first connection portion 11B inthis modification, it is possible to prevent problems such as a problemthat the permanent magnet 11Ba and the second connection portion 23Ccome into contact with each other thus causing wear of the permanentmagnet 11Ba and the second connection portion 23C, or a problem that thepermanent magnet 11Ba is exposed to the inner space S1 thus causingcorrosion of the permanent magnet 11Ba. Further, the entire end surfaceof the diaphragm 12 a on the flow passage unit 20 side is covered by thecover portion 11Bb and hence, the diaphragm 12 a can be protected. It isalso possible to prevent a problem that the permanent magnet 11Ba ispeeled off from the diaphragm 12 a.

Fifth Embodiment

Next, a pressure detection device according to a fifth embodiment of thepresent disclosure is described with reference to drawings.

The fifth embodiment is a modification of the first embodiment.Hereinafter, unless otherwise specified below, the fifth embodiment isassumed equal to the first embodiment so that the same constitutionalelements are given the same reference characters, and the description ofsuch constitutional elements is omitted.

The pressure detection device of the fifth embodiment differs from thepressure detection device of the first embodiment with respect to apoint that a second connection portion 23D is integrally formed with thediaphragm 22 by insert molding.

As shown in FIG. 11, in the pressure detection device of thisembodiment, a portion of the second connection portion 23D on the flowpassage 21 a side is formed into a shape where an upper end portion hasa large diameter about the axis Y1, and a portion below the upper endportion has a smaller diameter about the axis Y1 than the upper endportion. Further, the second connection portion 23D is integrally formedwith the diaphragm 22 made of a resin material by insert molding.

In the pressure detection device of this embodiment, the secondconnection portion 23D is integrally formed with the diaphragm 22 sothat it is unnecessary to join the second connection portion 23D to thediaphragm 22 by an adhesive agent or by thermal welding. Accordingly,compared to the case where the second connection portion 23D is joinedto the diaphragm 22, it is possible to reduce a manufacturing cost inmanufacturing a pressure detection device.

Sixth Embodiment

Next, a pressure detection device according to a sixth embodiment of thepresent disclosure is described with reference to drawings.

The sixth embodiment is a modification of the first embodiment.Hereinafter, unless otherwise specified below, the sixth embodiment isassumed equal to the first embodiment so that the same constitutionalelements are given the same reference characters, and the description ofsuch constitutional elements is omitted.

The pressure detection device 100 of the first embodiment is configuredsuch that the first connection portion 11 is joined to the surface ofthe diaphragm 12 a which is in contact with the inner space S1. On theother hand, in the pressure detection device of this embodiment, thefirst connection portion 11B is joined to a surface of the diaphragm 12a which is not in contact with the inner space S1.

As shown in FIG. 12, in the pressure detection device of thisembodiment, the first connection portion 11B formed into a cylindricalshape using a permanent magnet is joined to the surface of the diaphragm12 a which is not in contact with the inner space S1. The through hole12 b is formed in the surface of the diaphragm 12 a which is not incontact with the inner space S1, and the through hole 12 b maintains apressure applied to the surface of the diaphragm 12 a at an atmosphericpressure. In this embodiment, the first connection portion 11B isdisposed in the through hole 12 b so as to prevent the inner space S1from increasing.

In the pressure detection device of this embodiment, the firstconnection portion 11B is joined to the surface of the diaphragm 12 a onthe side which is not in contact with the inner space S1. Further, inthe pressure detection device of this embodiment, a second connectionportion 23E is joined to the surface of the diaphragm 22 on the sidewhich is in contact with the inner space S1. With such a configuration,in removing the flow passage unit 20 from the pressure detection unit10, a magnetic force in the direction that the first connection portion11B approaches the diaphragm 12 a acts on a portion where the firstconnection portion 11B and the diaphragm 12 a are joined to each other.This is because the first connection portion 11B generates a magneticforce of attracting the second connection portion 23E. Accordingly,compared to the case of the first embodiment where the first connectionportion is joined to the surface of the diaphragm 12 a on the side whichis in contact with the inner space S1, it is possible to prevent, by theaction of a magnetic force, a problem that the first connection portionis peeled off from the diaphragm 12 a.

Further, the first connection portion 11B is disposed in a spaceisolated from the inner space S1 by the diaphragm 12 a. With such aconfiguration, there is no possibility that a manipulator inadvertentlycomes into contact with the portion where the first connection portion11B and the diaphragm 12 a are joined to each other. Accordingly, it ispossible to prevent a problem that the first connection portion 11B ispeeled off from the diaphragm 12 a due to carelessness of themanipulator.

Another Embodiment

In the description made heretofore, the flow passage unit 20 includesthe flow passage body 21 and the diaphragm 22 joined to the flow passagebody 21. However, another mode may be adopted.

For example, the flow passage unit 20 may be formed such that the flowpassage body 21 and the diaphragm 22 are formed into one integral bodyusing a single material.

The invention claimed is:
 1. A pressure detection device comprising: apressure detection unit configured to detect a pressure transmitted to apressure detecting portion; a flow passage unit in which a flow passagefor introducing a fluid is formed; and a mounting mechanism configuredto detachably mount the flow passage unit on the pressure detectionunit, wherein the pressure detection unit includes: a pressure sensorincluding the pressure detecting portion; and a first connection portionjoined to the pressure detecting portion, the flow passage unitincludes: a pressure receiving portion configured to be displaced byreceiving a pressure of the fluid flowing through the flow passage; anda second connection portion joined to the pressure receiving portion,one of the first connection portion and the second connection portion isformed of a magnet, and the other of the first connection portion andthe second connection portion is formed of a magnet or a magnetic body,the mounting mechanism comprises a first fastening member mounted on theflow passage unit and a second fastening member mounted on the pressuredetection unit, the first connection portion that is joined to thepressure detecting portion of the pressure detection unit and the secondconnection portion that is joined to the pressure receiving portion ofthe flow passage unit are brought into contact with each other byfastening the first fastening member to the second fastening member, andin a state where the flow passage unit is mounted on the pressuredetection unit by the mounting mechanism, the first connection portionand the second connection portion are disposed in a state where thefirst connection portion and the second connection portion are attractedto and brought into contact with each other by a magnetic force, thesecond connection portion is disposed in an inner space defined by thepressure receiving portion and the pressure detecting portion, the firstconnection portion is joined to a surface of the pressure detectingportion which is not in contact with the inner space, and in the statewhere the flow passage unit is mounted on the pressure detection unit bythe mounting mechanism, the first connection portion and the secondconnection portion are disposed in the state where the first connectionportion and the second connection portion are attracted to each other bythe magnetic force with the pressure detecting portion interposedbetween the first connection portion and the second connection portion.2. The pressure detection device according to claim 1, wherein the firstconnection portion is formed of the magnet, and the second connectionportion is formed of the magnetic body.
 3. The pressure detection deviceaccording to claim 1, wherein an end surface of the first connectionportion on a side of the flow passage unit is formed to have a planarshape, and an end surface of the second connection portion on a side ofthe pressure detection unit is formed to have a spherical shape whichprojects toward the first connection portion.
 4. The pressure detectiondevice according to claim 2, wherein an end surface of the firstconnection portion on a flow passage unit side is formed to have aplanar shape, and an end surface of the second connection portion on apressure detection unit side is formed to have a spherical shape whichprojects toward the first connection portion.
 5. The pressure detectiondevice according to claim 1, wherein the pressure detection unit has acommunication flow passage configured to make an inner space defined bythe pressure receiving portion and the pressure detecting portion and anouter space maintained at an atmospheric pressure communicate with eachother.
 6. The pressure detection device according to claim 1, whereinthe pressure sensor outputs a pressure signal which corresponds to adeformation of the pressure detecting portion according to a change of apressure transmitted to the pressure detecting portion.
 7. The pressuredetection device according to claim 1, wherein in the state where theflow passage unit is mounted on the pressure detection unit by themounting mechanism, the first connection portion and the secondconnection portion are disposed in the state where the first connectionportion and the second connection portion are attracted to and broughtinto direct contact with each other by the magnetic force.
 8. Thepressure detection device according to claim 1, wherein in the statewhere the flow passage unit is mounted on the pressure detection unit bythe mounting mechanism, the first connection portion and the secondconnection portion are disposed in the state where the first connectionportion and the second connection portion are attracted to and broughtinto contact with each other, via at least one cover portion, by themagnetic force.
 9. A pressure detection device comprising: a pressuredetection unit configured to detect a pressure transmitted to a pressuredetecting portion; a flow passage unit in which a flow passage forintroducing a fluid is formed; and a mounting mechanism configured todetachably mount the flow passage unit on the pressure detection unit,wherein the pressure detection unit includes: a pressure sensorincluding the pressure detecting portion; and a first connection portionjoined to the pressure detecting portion, the flow passage unitincludes: a pressure receiving portion configured to be displaced byreceiving a pressure of the fluid flowing through the flow passage; anda second connection portion joined to the pressure receiving portion,one of the first connection portion and the second connection portion isformed of a magnet, and the other of the first connection portion andthe second connection portion is formed of a magnet or a magnetic body,in a state where the flow passage unit is mounted on the pressuredetection unit by the mounting mechanism, the first connection portionand the second connection portion are disposed in a state where thefirst connection portion and the second connection portion are attractedto each other by a magnetic force, the second connection portion isdisposed in an inner space defined by the pressure receiving portion andthe pressure detecting portion, the first connection portion is joinedto a surface of the pressure detecting portion which is not in contactwith the inner space, and in the state where the flow passage unit ismounted on the pressure detection unit by the mounting mechanism, thefirst connection portion and the second connection portion are disposedin the state where the first connection portion and the secondconnection portion are attracted to each other by the magnetic forcewith the pressure detecting portion interposed between the firstconnection portion and the second connection portion.